Process of devulcanizing gums.



UNITED STATES PATENT OFFICE.

PAUL HENRI JOSEPH OHAUTARD AND HENRI KESSLER, OF PARIS, FRANCE.

PROCESS OF DEVU'LCANIZING GUMS.

SPECIFICATION forming part of Letters Patent No. 722,944, dated March 1'7, 1903. Application filed April 23,1902. Serial No. 104.414.. (No specimens.)

To all whom it may concern..-

Be it known that we, PAUL HENRI J osEPu crating vulcanized caoutchouc or rubber, as

well as other gum'ssuch as gotta-percha, for example.

In order to regenerate vulcanized rubber, it is necessary to practically separate therefrom the sulfur incorporated with the rubber in the vulcanizing process and which exists in the vulcanized mass in astate of combination with the gum or as simply mixed therewith.

The object of the invention is to effect the regeneration of the gum in such a manner that the latter shall be in condition for use as raw rubber or for revulcanization and also to efiect this regeneration at such a cost as will effect a material economy.

In carrying out our invention we employ as a solvent for the vulcanized gum any substance which will at the same time dissolve both the caoutchouc and the sulfur. We profor for this purpose some one of the phenols, either pure or mixed; but creosote and other solvents maybe used. By operating in vacuo vulcanized caoutchouc may be dissolved by such a substance as that named above at a temperature not exceeding 100 centigrade. In the operation the sulfur separates partly in the condition of dissolved sulfur and partly in the condition of a component of volatile mass or soluble compounds. Owing to the low temperature at which the operation is effected, the gum is regenerated without undergoing modifications or changes of a kind to afiect its commercial value. After dissolving the vulcanized rubber the solvent and the sulfur are separated from the rubber and the latter thoroughly washed. This regenerated rubber is readily soluble in benzin, while vulcanized rubber is not, and the regenerated rubber may be vulcanizedanew.

By way of illustration we will describe the preferred method of carrying out our invention in practice in regenerating ordinary vulcanized rubber.

In a suitable boiler adapted for operation in 'vacuo we put one hundred kilos of vulcanized rubber reduced to bits or fragments and about five hundred kilos of ordinary commercial phenol or phonic acid. A vacuum is established in the boiler sufficient to reduce the pressure by about seventy to seventy-two centimeters. The mass is then heated to boiling, which is at a temperature of about 100 centigrade, and is at the same time mechanically agitated. The boiler is put in communication with a reflux condenser and the boiling kept up until the solution is complete. This first step in the treatment varies somewhat in duration according to the character of the waste rubber treated, the relative proportions of the solvent and waste rubber, the temperature, and the pressure in the boiler.

After the solution has been efiected as above described the boiler is put in communication with an ordinary condenser and most of the phenol distilled off. Part of the sulfur will have been removed by the aspirator in the gaseous products; but there will remain in the mass a part in the form of free dissolved sulfur and in the state of sulfur compounds. This sulfur may be eliminated in the state of insoluble lead sulfid, for example, or by employing a suitable solvent or by precipitation. Whatever means may be employed, the sulfur separated from the gum will be removed. The remaining phenol is now separated from the gum. This may be eifected by using a solvent of the phenol, such as alcohol, or by using a combining agent, such as soda or lye, or by both of these treatments. Finally the mass is run into a vat, where the gum is collected and thoroughly washed. This washed gum may then be used for any of the purposes for which raw rubber is commonly used.

Where other solvents than phenol are employed, the process will be substantially the same, only the temperature and pressure being somewhat modified.

The application of the above described process to damaged gums and to crude guttapercha yields excellent results, the product being pure and unchangeable.

It will be noted that our process for regencrating vulcanized rubber and gotta-percha consists, essentially, in desulfurizing by dis solving them in some solvent, such as phenol or creosote, which will dissolve both the sulfur and gum, this operation being performed in cacao at a temperature ordinarily not exceeding 100 centigrade.

Having thus described our invention, we claim- 1. The herein-described methodof regenerating vulcanized gums, which consists in dissolving the same in vacuo at a temperature not exceeding 100 centigrade, in phenol, then distilling ofi the main portion of the phenol, and then removing the separated sulfur and remaining phenol.

2. The herein-described method of regenerating vulcanized rubber, which consists in mixing the latter with phenol in about the PAUL HENRI JOSEPH CHAUTARD. HENRI KESSLER.

Witnesses:

J ULES ARMENGAUD, J eune, EDWARD P. MACLEAN. 

